NATURAL AND IMMUNE ANTIBODIES 151 



LiPOiDOPHiLic Reagins. — Tlicsc are antibody-like siilistaiicos tliat 

 will sensitize emulsions of certain tissne lipoids in tlie same way 

 that bacteria are sensitized by their specific antibody. Just as 

 sensitized bacteria may become agglutinated or may unite witli 

 complement, so will sensitized lipoid particles undergo agglutina- 

 tion if conditions are appropriate or they will combine with the 

 complement if it is present. In man, i-eagins for acetone insoluble 

 lipoids obtained from heart muscle or other animal tissue are 

 found almost exclusively in the blood during the secondary and 

 later stages of syphilis. A somewhat similar reagin, found occa- 

 sionally in nonsyphilitics and ciuite extensively in the blood of the 

 lower animals, can apparently be differentiated from syphilitic 

 reagin by methods to be discussed in a later chapter. 



Precipitins. — These are antibodies produced against any un- 

 altered soluble protein. They are usually found in tlie l)lood of 

 any man or lower animal that has received injections of foreign 

 protein as, e.g., antitoxin, normal horse serum, bacterial extracts, 

 etc. The antibody sensitizes each colloidal particle of protein and 

 this leads to a precipitation of these sensitized colloidal particles 

 and to the union with complement if it is present. 



Anaphylactic Sensitizers. — Many persons have considered 

 these interesting antibodies as identical with the ])recipitins but 

 more recently some doubt has been cast upon this hypothesis. They 

 are antibodies that have the rather unique property of attaching 

 them.selves to smooth muscle and other tissue cells of the animal 

 which produce them, several days after they make their appearance 

 in the blood stream. This is rather a serious state of affairs for 

 the animal, because on receiving another injection of antigen it 

 would combine with these antibodies that are attached to the body 

 cells and produce a serious physiological reaction called anapJwj- 

 lactic shod'. 



Antitoxins.- — When a specific antigenic poison such as diph- 

 theria toxin, tetaniLS toxin, l)otulinus toxin or streptococcus scarlet 

 fever toxin is injected into an animal, a specific neutralizing anti- 

 body called antitoxin is developed for the particular kind of toxin 

 injected. It neutralizes but does not destroy the toxin. Small 

 amounts of antitoxins may be found in some normal animals and 

 in man. 



